αvβ6 integrin is required for TGFβ1-mediated matrix metalloproteinase2 expression

Transforming growth factor (TGF) β1 activity depends on a complex signalling cascade that controls expression of several genes. Among others, TGFβ1 regulates expression of matrix metalloproteinases (MMPs) through activation of Smads. In the present study, we demonstrate for the first time that the αvβ6 integrin interacts with TGFβ receptor II (TβRII) through the β6 cytoplasmic domain and promotes Smad3 activation in prostate cancer (PrCa) cells. Another related αv integrin, αvβ5, as well as the αvβ6/3 integrin, which contains a chimeric form of β6 with a β3 cytoplasmic domain, do not associate with TβRII and fail to show similar responses. We provide evidence that αvβ6 is required for up-regulation of MMP2 by TGFβ1 through a Smad3-mediated transcriptional programme in PrCa cells. The functional relevance of these results is underscored by the finding that αvβ6 modulates cell migration in an MMP2-dependent manner on an αvβ6-specific ligand, latency-associated peptide (LAP)-TGFβ. Overall, these mechanistic studies establish that expression of a single integrin, αvβ6, is sufficient to promote activation of Smad3, regulation of MMP2 levels and consequent catalytic activity, as well as cell migration. Our study describes a new TGFβ1-αvβ6-MMP2 signalling pathway that, given TGFβ1 pro-metastatic activity, may have profound implications for PrCa therapy.